Toxicity of the readily leachable fraction of urban PM2.5 to human lung epithelial cells: Role of soluble metals.

Fine airborne particulate matter (PM2.5) has been repeatedly associated with adverse health effects in humans. The PM2.5 soluble fraction, and soluble metals in particular, are thought to cause lung damage. Literature data, however, are not consistent and the role of leachable metals is still under debate. In this study, Winter and Summer urban PM2.5 aqueous extracts, obtained by using a bio-compatible solution and different contact times at 37 °C, were used to investigate cytotoxic effects of PM2.5 in cultured lung epithelial cells (A549) and the role played by the leachable metals Cu, Fe, Zn, Ni, Pb and Cd. Cell viability and migration, as well as intracellular glutathione, extracellular cysteine, cysteinylglycine and homocysteine concentrations, were evaluated in cells challenged with both PM2.5 extracts before and after ultrafiltration and artificial metal ion solutions mimicking the metal composition of the genuine extracts. The thiol oxidative potential was also evaluated by an abiotic test. Results demonstrate that PM2.5 bioactive components were released within minutes of PM2.5 interaction with the leaching solution. Among these are i) low MW (<3 kDa) solutes inducing oxidative stress and ii) high MW and/or water-insoluble compounds largely contributing to thiol oxidation and to increased homocysteine levels in the cell medium. Cu and/or Ni ions likely contributed to the effects of Summer PM2.5 extracts. Nonetheless, the strong bio-reactivity of Winter PM2.5 extracts could not be explained by the presence of the studied metals. A possible role for PM2.5 water-extractable organic components is discussed.

Environmental concentrations of fibers with fluoro-edenitic composition and population exposure in Biancavilla (Sicily, Italy).

INTRODUCTION: The town of Biancavilla (Sicily) was included in the National Priorities List of Contaminated Sites due to environmental dispersion of amphibole fibers owing to the extraction of materials from a local quarry. The present report summarizes results from several, hitherto unpublished, environmental surveys carried out in the area, as well as from published analyses of the chemistry and composition of fibers. METHODS: Data included here comprises environmental fiber concentrations by scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) analysis in soil, indoor and outdoor air, personal monitoring, as well as a chemical characterization of the fibers. The full chemical structure and spectroscopic characterization of fibers were obtained through a multi-analytical approach: SEM-EDS, X-ray powder diffraction (XRPD), as well as Mössbauer (MS) and Fourier transform infrared (FT-IR) spectroscopies. RESULTS: Data analyzed provided a spatial and temporal picture of fiber concentrations in Biancavilla, and a qualitative assessment of population exposure. Results suggest that until 2000, the population had been exposed to high levels of amphibole fibers. Mitigation measures adopted since 2001, gradually reduced exposure levels to about 0.1-0.4 ff/l. Previous studies on fibrous amphiboles from Biancavilla reported considerable chemical variability. Differences in composition, especially concerning the presence of Si, Ca, Fe, and Na, were found both within and between samples. Compared to the previously investigated prismatic fluoro-edenite, these fibrous fluorine amphiboles consistently showed higher average values of Si and Fe content, whereas Ca was significantly lower, which we consider a distinctive characteristic of the fluorine fibrous variety. CONCLUSIONS: The population of Biancavilla had been highly exposed to a suite of fibrous amphiboles for over 50 years. Dust mitigation measures have gradually reduced exposure, but continuous environmental follow-up is necessary in order to monitor exposure levels and prevent adverse health effects for future generations.

Quantitative energy dispersive X-ray analysis of submicrometric particles using a scanning electron microscope.

The quantitative scanning electron microscope-energy dispersive X-ray (SEM-EDX) analysis of a horneblende and two augite prismatic samples reduced to submicrometric particles was performed, and error due to the particle effects ("absent mass" and the "reduced absorption" effect) was minimized. Correction factors as a function of fragment size were obtained for O, Na, Mg, Si, Ca, and Fe. In addition, the influence of chemical composition of the samples used as standards (the matrix effect) on correction factors was evaluated. The results indicate that the absent mass effect is dominant for all elements except for the light elements O and Na, for which the reduced absorption effect is dominant. No significant matrix effect has been observed. By using corrected SEM-EDX data, the error on quantification of the element concentration has been estimated to be 3% relative for light elements and below 2% relative for heavy elements (notably, about 1% relative for Fe).